The present invention pertains generally to needled sutures. More particularly, the invention relates to the utilization of a shrink sleeve heat shrunk-fit to couple together a needle and a suture. A shrink sleeve or shrink sleeves might additionally be utilized to couple a needle and a number of sutures for providing a linked tandem suture or a controlled release suture or for linking a number of sutures.
There exist in the art a variety of teachings pertaining to the attachment of a suture to a suture needle. Exemplary of needle suture connection might be the placement of an end of a suture into a hole or channel in the blunt end of a needle whereinafter the hole or channel is mechanically swaged or crimped onto the suture so that the suture is firmly held within the needle. Another teaching for anchoring a suture to a needle might be the placement of a suture tip into a recess in the blunt end of a needle whereafter the needle is heated to expand the suture tip within the recess into tight engagement with the recess walls. Yet another teaching for connecting a needle and a suture might be by means of a needle shank portion of smaller diameter than the needle diameter, with the shank being inserted into an internal or central bore provided in the suture for tight fitting engagement and anchoring therein. Still another teaching to effect a needle-suture connection might be the use of the techniques of heating, soldering, brazing or gluing a hollow metal tubular suture for coupling the tubing to a surgical needle. Another teaching might be the use of an eyeless surgical needle in the butt end of which is an opening wherein a flexible suture leader is crimped and a connector sleeve of high strength metal is crimped to capture a surgical suture.
Suture needles are formed from a relatively soft metal wire-like material. A segment of wire of sufficient length for both the needle and a handle (for holding the needle during the manufacture thereof) is cut from the main wire source. The length is then straightened, formed with a point at the front end, and a part of the shank to the rear of the point may be flattened to provide a place for the surgeon to grip the needle.
When using the channel method for attaching the suture to the needle, a channel is formed in the needle, rearward of the shank while the needle is still in its initial, relatively soft condition. This groove is stamped into the needle by means of a V-shaped die. The V-shape of the die is necessary to assure that a sufficient force is concentrated at the appropriate place on the channel to form a groove of a sufficient depth without damaging the walls of the newly formed channel.
The needle shaft is now bent to the desired curvature and the needle is hardened. This may be accomplished by placing the needles into a vacuum furnace at approximately 980.degree. C. to 1040.degree. C. followed by tempering at about 260.degree. C. to take out the brittleness. The finished needle may have a Rockwell hardness of approximately 49 to 55.
Since the suture could not withstand the heat treatments, it must of course be attached to the needle after hardening. However, it is impossible to bend the hardened channel walls to close them onto a suture without cracking or twisting the walls. Thus, before closing the channel walls onto suture it is necessary to soften the channel walls by annealing. Of course, care must be taken to prevent the softening effect of the annealing procedure from being felt forward of the channel walls along the shank or the needle point.
Following annealing the needle is electroplated, and the handle part is chopped off leaving the channel open to the rear. The suture is then inserted and the channel walls are closed onto the suture, preferably by crimping to hold the suture.
Notwithstanding the necessity of the annealing procedure, it has been found that annealing has several detrimental effects. First, there is an inevitable drift of heat down the shank of the needle causing some undesirable annealing effect on the shank of the needle itself. In addition, the annealing process invariably decreases the "stainlessness" of the needle, that is the ability of the needle to resist rust, especially at the softened channel.
Further, the "chop off" of the handle from the main part of the needle is less clean with a softer annealed needle than with a harder needle. This "chop off" is accomplished through that portion of the needle which has the channel formed into it. The harder the material of the channel, the cleaner the chop off, and the smaller the resultant burr. The annealing process, by softening the channel, prevents a clean chop off and makes it more likely for burrs to occur.
Moreover, the above disadvantages can become even more significant when the needle is treated to obtain a very high Rockwell hardness. In this case it may be necessary to anneal the needle several times, thereby significantly increasing the above noted undesirable effects.
Indeed, with a very hard needle, it is frequently impossible or difficult to accomplish the necessary softness for bending the needle material without cracking or twisting the same regardless of the number of annealing steps.
Thus, there exists a need for improvements which will permit the use of a superior means for attaching a suture to a needle while eliminating or substantially reducing the detrimental effects of annealing.
Accordingly, herein disclosed is the coupling of a needle to a suture and a suture to a suture by means of a heat shrinkable sleeve which has numerous advantages over known couplings. Specifically, attachment time is significantly less, handling and equipment costs are reduced, needle quality is improved, needle to suture and suture to suture attachment is enhanced, and a more economical needle to suture and suture to suture coupling means is presented.